[impala] 02/02: IMPALA-10989: fix race for result set metadata

[jo...@apache.org]

This is an automated email from the ASF dual-hosted git repository.

joemcdonnell pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/impala.git

commit 8ddac48f3428c86f2cbd037ced89cfb903298b12
Author: Joe McDonnell <jo...@cloudera.com>
AuthorDate: Mon Feb 7 15:27:35 2022 -0800

    IMPALA-10989: fix race for result set metadata
    
    TSAN tests uncovered a race condition between the
    thread reading the result set metadata in
    ImpalaServer::GetResultSetMetadata() and the
    thread setting the result set metadata in
    ClientRequestState::SetResultSet() from
    ClientRequestState::ExecDdlRequestImpl().
    This is introduced by IMPALA-10811, which runs
    ExecDdlRequestImpl in an async thread that
    can now race with the client thread.
    
    GetResultSetMetadata() holds ClientRequestState's
    lock_ while reading the result set metadata, so
    the fix is to hold this lock when writing the
    result set metadata.
    
    Testing:
     - Ran TSAN core job
    
    Change-Id: Ic0833ed20d62474c434fa94bbbf8cd8ea99a7cf4
    Reviewed-on: http://gerrit.cloudera.org:8080/18212
    Tested-by: Impala Public Jenkins <im...@cloudera.com>
    Reviewed-by: Csaba Ringhofer <cs...@cloudera.com>
---
 be/src/service/client-request-state.cc | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/be/src/service/client-request-state.cc b/be/src/service/client-request-state.cc
index ca0f6c0..af68245 100644
--- a/be/src/service/client-request-state.cc
+++ b/be/src/service/client-request-state.cc
@@ -721,8 +721,12 @@ void ClientRequestState::ExecDdlRequestImpl(bool exec_in_worker_thread) {
         ExecQueryOrDmlRequest(exec_request_->query_exec_request, !exec_in_worker_thread));
   }
 
-  // Set the results to be reported to the client.
-  SetResultSet(catalog_op_executor_->ddl_exec_response());
+  // Set the results to be reported to the client. Do this under lock to avoid races
+  // with ImpalaServer::GetResultSetMetadata().
+  {
+    lock_guard<mutex> l(lock_);
+    SetResultSet(catalog_op_executor_->ddl_exec_response());
+  }
 }
 
 bool ClientRequestState::ShouldRunExecDdlAsync() {